Pyroclastic rocks / Пирокластические породы

Volcanic eruptions are spectacular natural events that have piqued man's curiosity since prehistoric times. On the one hand they can be of great benefit to man, but on the other can cause great harm and thereby provide a major impetus to their study. Broader aspects make use of volcanoes as windows into the interior of the earth. Magma, molten rock, provides one of the major clues to the earth's origin and to the evolution of its mantle and crust. Our planet's hydrosphere and atmosphere - and thus the origin and evolution of life - owe their origin to degassing of the earth, a process largely accomplished by volcanic eruption. Periods of especially intense volcanic activity can affect climate and thus the world's flora and fauna. Volcanic rocks are the source material from which many sedimentary and metamorphic rocks are derived.